Colloidal dispersion of dextran for finishing textiles



COLLOIDAL DISPERSION OF DEXTRAN FOR FINISHING TEXTILES Leo J. Novak,Walter S. Hogue, and Howard J. Homer,

Dayton, Ohio, assignors to The Commonwealth Enginearing Company of Ohio,Dayton, Ohio, a corpora tion of Ohio No Drawing. Application June 18,1953, Serial No. 362,664

4 Claims. (Cl. 106-462) This invention relates to the sizing andfinishing of nbrous materials. More particularly, it relates to alaundry treating agent adapted for use by commercial laundries and inthe home as an ironing aid which imparts an attractive finish or hand tofibrous materials.

Raw starch has been, and is, the substance most widely used in thesizing and finishing of cotton textile goods. The major drawback of rawstarch is that it is neither soluble nor uniformly dispersible in waterat ordinary temperatures and, therefore, it must be mixed with water andpro-cooked to obtain a dispersion useful as such or after suitabledilution as a sizing medium for the cotton goods. If the raw starch issupplied to the ultimate user in the dry lump or powder form, thepre-cooking to effect adequate dispersion thereof in the water iscarried out by the user, for instance by the housewife, and is not onlyinconvenient and time-consuming, usually requiring from to minutes attemperatures of 55 C.100 (3., but also presents a hazard in that thecooking must be controlled to avoid under-degradation orover-degradation of the starch, which conditions result in excessivepenetration of the size into the fibers and yarns of the fabric withlittle or no protecting film of the size left on the fabric surface, orto undue sticking of the iron when the sized fabric is pressed with ahot iron. In addition, during the cooking step, the starch granules tendto swell and then rupture, so that much of the stiffnessimpartingproperty of the substance is lost upon subsequent ironing of the fabricsized therewith.

In an attempt to avoid these diificulties it has been proposed to usepartially cooked or raw starch in admixture with cold water. Sinceuncooked or only partially cooked starch is not readily and uniformlydispersed in water, the granules have a tendency to aggregate and themixtures require skill in their application and continuous agitationbefore and during application thereof in order to avoid settling andpacking of the starch. Even when great care is exercised it is foundthat when fabrics are treated with a mixture of cold water and a raw orpartially cooked starch, the aggregates which inevitably form arenon-uniformly distributed on the fabric. When the fabric carrying theaggregates is ironed, the aggregates appear as visible white streaks orblotches.

It has also been proposed to render starches soluble or dispersible inwater by cooking them in the course of their preparation for marketing.During such cooking, precautions must be taken to guard against bothundercooking and over-cooking of the starch. The available pre-cookedstarches are only poorly dispersible in water at room temperature, tendto ball up and form clumps which must be broken up by prolongedstirring. and invariably yield weak sols. v

In another attempt to solve the problem involved in the use of starch asa laundry size or stiffener, so-called liquid starches have beenmarketed. These comprise a dispersion of cooked starch in water or acomposition consisting essentially of cooked starch dispersed inan nitedStates Patent Patented July 24, 1956 aqueous medium by means of anemulsifying agent. However, as is well known, these prepared liquidstarches have proved to be unsatisfactory in many instances and mostlybecause their stiifness-imparting properties have been greatly reducedin the cooking process.

It may be stated, then, that no wholly satisfactory starch product is atpresent available for use as a size and which does not involve aprolonged cooking either by the supplier of the size or by the ultimateuser in laundry plants or the like or in the home.

It is an object of this invention to provide a new and improved sizingand stiffening agent for fibrous materials such as fabrics, garments,yarns, paper, etc. which has the stiffening and sizing properties ofstarch but which is soluble or dispersible in water at ordinary roomtemperatures without pre-cooking thereof.

Another object is to provide a sizing and stiffening agent which isdirectly soluble or dispersible in water at ordinary temperatures in awide range of concentrations.

A further object is to provide a sizing or stiffening agent which can beshipped in dry, particulate conditions and dissolved or dispersed inwater at room temperature, without pre-cooking by either the supplier oruser, to obtain a sizing or stiffening bath of any suitableconcentration between 0.1% and 20% by weight.

Another object is to provide a simple, relatively inexpensive method forsizing and stiffening fibrous materials including fabrics, garments,paper and the like.

These and other objects are accomplished by the present invention inaccordance with which there is provided a sizing and stiffening agentcomprising a water-soluble or water-dispersible dextran.

The dextrans are high molecular weight, balanced polysaccharidescomprising anhydroglucopyranosidic units joined by alpha-1,6 andnon-alpha-l,6 molecular structural repeating linkages and at least 50%of which linkages are, apparently, alpha-1,6 linkages. The properties ofthe dextrans, including the molecular structural repeating alpha-1,6 tonon-alpha-1,6 linkages ratios, the molecular weight, and the sensitivityto water, vary widely and a large number of dextrans which diflierspecifically with respect to these various properties are now known.

According to the present invention, it is found that fibrous materialscan be sized and stifiened effectively and conveniently by the use ofsubstantially pure dextrans having a range of molecular structuralrepeating alphal,6 to non-alpha-1,6 linkages ratios between 1.9:1 and30:1, a molecular weight of from 5,000 to x10 as determined bylight-scattering measurements, and a solubility or dispersibility inwater such as to form colloidally stable, aqueous solutions ordispersions of from 0.5% to 50% by weight concentration at ordinarytemperatures.

The present invention is not dependent on the method by which thedextran having the required combination of characteristics is obtained.It may be produced microbiologically, for example by inoculating, withsuitable selected bacteria, a sucrose-bearing medium containingparticular nitrogenous substances and certain inorganic salts. Forinstance, the dextran may be obtained by inoculating a medium containing5-10% of sucrose, 0.5% peptone, 0.5% dipotassium phosphate, 0.1% ofsodium chloride and 0.005% of manganous sulfate With Leuconostocmesenteroides B-512 (Northern Regional Research Laboratoryclassification), and incubating the inoculated medium at the temperaturemost favorable to the selected'microorganism until the maximum amount ofdextran is produced, after which the dextran may be precipitated fromthe culture medium by the addition of acetone or a water-miscible loweraliphatic alcohol, such as methanol, ethanol, isopropanol thereto. Orthe dextran may be obtained by cultivating a selected bacterium, such asLeuconoszoc mesentcroides B-512 to obtain a dextran-producing enzyme,separating the dextran from the medium in which the bacterium iscultivated, and introducing the enzyme into a medium in which dextran isformed by the action of the enzyme. The dextran may also be produced bymethods involving the bacterial conversion of 1,4 linkages of dextrinsto the 1,6 bonds of dextran, or by any other feasible method.

However the dextran to be used as the sizing or stiffening agent isobtained, it is important that it be in pure or substantially purecondition to avoid staining of the sized fibrous material thereby.Dextran produced microbiologically as described above should besubstantially free from nitrogenous substances, bacteria and enzymeprecipitated from the fermentate with it. Such impurities may be held toa minimum by controlling the conditions of the initial precipitation.Thus, a relatively pure dextran can be precipitated from the fermentateobtained by incubation of the culture medium inoculated with Leuconostocmesenteraides B-512 by adding alcohol to the fermentate at a pH of 2.5to 4.5. The dextran thus precipitated may be further purified by one ormore additional precipitations with the lower aliphatic alcohol or withacetone.

The dextran thus produced is a so-called native dextran which is solublein water, has a molecular structural repeating alpha-1,6 tonon-alpha-l,6 linkages ratio of 19:1 and a high molecular weightcalculated to be in the millions. It may be dried, as by drum drying, toobtain a fluffy product usable as such or after reduction to a powder,in preparing the present sizing bath. Other dextrans of similar highmolecular weight may also be used, or the dextran may have a lowermolecular Weight in the range stated previously herein. The lowermolecular weight dextrans may be obtained by hydrolysis of the highermolecular weight materials, as by means of acid or enzymatically,followed by fractionation, if desired, and such purification as may berequired to obtain a substantially pure, non-staining dextran.

Very advantageously, the size may comprise low molecular weight dextranfragments obtained in the conventional production of clinica dextran andwhich have hitherto been discarded as waste material. Such wasteproducts usually have an average molecular weight between 5,000 and50,000.

The dextran may be an initially water-soluble dextran obtained using themicroorganisms bearing the following NRRL classifications: Leuconostocmesenteroides B419, B-l146 and B4190, and which may or may not behydrolyzed to lower molecular weight. Or it may be an initiallywater-insoluble or substantially water-insoluble dextran obtained usingthe microorganisms Leucolmstoc mesenteroides B-742, B4191, B-1196,13-1208, 13-1216, B-1120, 8-1144, B-523, StreptObacterium dextranicumB-1254 and Betabacterium vermiforme Bl139, these dextrans being used asobtained, after purification, if they are dispersible in water to therequired concentration, or being hydrolyzed to lower molecular weight,more readily water-dispersible or watersoluble products.

In sharp contrast to starch, the dextrans having the combination ofproperties described have the important advantage that as obtainedintially, or after hydrolysis, they are soluble or uniformly dispersiblein water Without cooking by either the supplier or ultimate user andthey may be shipped and sold in the dry condition. The advantage overraw starch is obvious. The need to precook the raw starch to effectsatisfactory dispersion thereof in water always presents the problemthat unless the pre-cooking is carried out under controlled conditions,the starch will be either under-degraded or over-degraded, both of whichconditions result in inadequate or unsatisfactory sizing of the fibrousbase. The pre-cooking is particularly hazardous when carried out in thehome and improper cooking is usually the cause of the common complaintabout sticking of the iron, and scorching, during ironing of thestarched article. Elimination of the cooking, as is possible when thesedextrans are used, eliminates both the cooking and sticking problems,and the supplier can exercise complete control over the properties ofthe sizing agent since, in use, the dextran is not exposed to haphazard,uncontrolled degradation by heat.

The concentration of the dextran in the aqueous sizing bath may bevaried widely, within the upper and lower limits of dispersibility orsolubility of the dextrans in water, and depending upon the particulardextran used. In general, aqueous baths containing 0.1% to 5.0% dextranare satisfactory when the dextran is a high molecular weight or nativeunhydrolyzed dextran. Aqueous baths containing up to 20% by weightdextran may be used when the dextran has a comparatively low molecularweight, i. e., when it is a hydrolyzed dextran or the by product lowmolecular weight fraction of clinical dextran production. Within theseranges, the dextran concentration may be selected for the type offibrous material to be sized, higher dextran water ratios being usefulfor such laundry as shirts and the like, and lower ratios beinggenerally preferred for sizing table linens, dresses, etc. The presenceof the dextran on the laundered article does not interfere with smoothironing thereof, and the stilfened, ironed article has a polished orglossy appearance and a soft or velvety touch. The dextran size orfinish, which adheres firmly to the cotton or other fibers, impedespenetration of soil or dirt into the fabric.

In this regard, it may be noted that the dextrans are particularlydesirable sizing or finishing agents for shirts or other articles to belaundered since these dextrans are anti-soil fixation agents whichfacilitate laundering of the article sized therewith. The dextranremoved from the fabric during laundering thereof functions to hold soilremoved in the washing operation in suspension so that the soil cannotredeposit on the article.

The following examples, in which the parts are by weight, areillustrative of specific embodiments of the invention.

Example I A sizing bath was prepared by simply dissolving one part of aparticulate pure, hydrolyzed dextran having a molecular weight of about100,000 and a molecular struc' tural repeating alpha-1,6 ton0n-alpha-1,6 linkages ratio of 10:1 in five parts of water at roomtemperature. The collar and cuffs of a freshly laundered white cottonshirt were immersed in the sizing bath for about one minute, removed,wrung out, and the shirt was ironed. The sized portions of the ironedshirt were stiffened and had a high, smooth polish.

Example [I A sizing bath was prepared by dissolving one part of asubstantially pure, native B-512 dextran in 20 parts of water, at roomtemperature. A white cotton. blouse was immersed in the bath for aboutfive minutes, removed, and wrung out. It carried a uniform film ofdextran and on drying and ironing acquired a stiff but full mellow hand.

Other dextrans, such as those having structural molecular repeatingalpha-1,6 to non-alpha-1,6 linkages ratios of 1.9:1, 3.521,8:1,15:1,16:1,18:1and 22:1 and molecular weights between 5,000 and thatof a native microbiologically produced dextran may be substituted in theExamples and give the same results.

As will be apparent, the molecular structural repeating alpha-1,6 tonon-alpha-1,6 linkages ratios, are independent of the molecular weightand dextrans of different molecular weights may have the same linkagesratio.

As is known, textile finishers of cotton goods often obfeet to starchfinishes as too stiff and harsh and prefer to utilize starchcompositions comprising special plasticizing agents, generally some typeof tallow which is usually sulfated and modifies the dryness andboardiness frequently imparted to cotton by starch. Instead of sulfatedtallow, sulfonated oils such as castor or olive oil and sulfated cetyland stearyl alcohols have been used. The dextrans do not requirecombination with these adjuvants since, under normal conditions, thefabrics sized with the dextrans in the absence of the plasticizers hassufficient soft ness and plasticity to be commercially acceptable.However, the dextran may be used in conjunction with plasticizing aids,or with wetting agents, emulsifiers, dispersants or the like, ifdesired.

The dextrans may be used as substitutes for laundry starch in the sizingand stiffening of cotton goods. They may also be used as sizing andfinishing agents for other materials, for instance in textile finishingtreatments performed in the mill, and may be used for purposes for whichstarch is not generally acceptable to the trade. Thus, it is well knownthat starch is not suitable for sizing and finishing regeneratedcellulose, silk and similar luxury fabrics designed and processed tohave luxurious appearance and softness of touch because starch filmsimpair the desired handle and detract from the high quality appearanceof those fabrics. The finishers have resorted to other finishes, such asfinishes of protein origin, glue, and synthetic resins. The proteinsizes have a tendency to yellow whites and to impart an odor to thefabrics, glue has a loading or weighting effect, and the syntheticresins must be carefully controlled both as to type, composition, anddegree of polymerization to avoid rendering the fabric so stiff andboardy, that it must be put through flexers to break up the resin filmor coating. In contrast to starch and the protein, glue or resinfinishes, the dextrans may be used to stiffen the so-called luxuryfabrics Without impairrnent and even for improvement of the feel orappearance and draping quality thereof, and thus have a much wider rangeof usefulness than raw or modified starch.

The substantially pure dextrans, which are odorless, non-staining,non-irritating substances may be used to size, stiffen or finish alltypes of fabrics, particularly cotton fabrics in concentrations between0.1% and 20% by weight, the concentration being selected on the basis ofthe molecular weight and to produce the desired stiffness, bulk andbody. The more highly concentrated dispersions, which may have aconsistency of or approximating a paste may be applied to the goods on apad or by means of a doctor blade, during finishing of the goods formarketing. These dextrans form smooth, uniform films or coatings on thesized fabrics, which effectively mask the reedy, irregular appearance ofmany types of cotton goods and that is, at best, imperfectly masked bystarch finishes. After ironing or pressing, the sized fabrics have asmooth, polished appearance and are substantially free from blotches orstreaks because of the homogeneity of the dextran dispersion appliedthereto and the absence of aggregates or balls from the dispersion. Itis found that goods sized with the dextrans disclosed herein may bedampened, prior to ironing thereof, and ironed in the damp condition,without effecting uniform distribution of dextran size or causing theiron to pick up the dextran from the fabric.

The dextrans may be used as size and finish for all types of fibrousmaterials. They may be used as the tub or coating size for paper, and asa warp size to coat and impregnate threads so as to strengthen them forweaving and the sizing medium for the threads may contain, in additionto the dextran, special lubricants which assist in preventing stickingof the threads to the drier rolls, as well as softeners, penetrants,preservatives and loading agents. The dextran sizing medium may beapplied to the warp threads on a slasher and has the important advantagethat it may be removed from the woven fabric prior to dyeing thereof, bysimply passing the fabric through a plain water bath whereas whenstarches are used, the fabric must be subjected to special scouringtreatments for removal of the size. The dextrans may also be used in thepure and backfill finishing of various types of textile fabrics. Used asa laundry starch, it may be applied to the fabrics in combination withbrighteners which exhibit effects similar to blueing.

This invention provides, for the first time, a starch substitute whichis soluble or uniformly dispersible in water at room temperature withoutpre-cooking thereof either in the course of its production or by theuser, which may be shipped in dry, particulate condition for directdispersion or dissolution in water at ordinary temperatures, which is atleast as effective as starch in sizing and finishing fibrous materialsand adapted to use in a wide range of concentrations which may be variedto obtain particular effects, and depending on the fabric treated. Itwill be understood, therefore, that while there have been describedcertain specific embodiments of the invention, it is not intendedthereby to limit or circumscribe it by the details given, in view of thefact that the invention is susceptible of various modifications andchanges within the scope of this disclosure and of the appended claims.

We claim:

1. As a finishing agent for textile materials to provide said materials,Without loss of the essential flexibility of the textile, and withoutthe application of starch thereto, with a smooth, glossy surface finishsubstantially free from streaks, blotches and discoloration onhot-pressing thereof after application of a solution of the finishingagent thereto, and drying of the textile, a substantially pure, dry,particulate dextran having a molecular weight of about 5000 to about50,000, as determined by light scattering measurements, a molecularstructural repeating alpha-l,6 to non-alpha-l,6 linkages ratio of 1.9:1to 30:1 and which forms, in water, and at ordinary temperatures,colloidally stable dispersions of from 0.5% to 50% by weightconcentration.

2. An aqueous finishing bath for textile materials consistingessentially of water and, dispersed therein, for providing the textilematerials, without loss of the essential flexibility thereof and withoutthe application of starch thereto, with a smooth, glossy surface finishsubstantially free from streaks, blotches and discoloration onhot-pressing thereof after application of the dispersion thereto anddrying of the textile, from 1% to 20% by weight of, a substantially puredextran having a molecular weight of about 5000 to about 50,000 asdetermined by light scattering measurements, a molecular structuralrepeating alpha-1,6 to non-alpha1,6 linkages ratio between 1.9:1 and30:1, and which forms, in water and at ordinary temperatures,colloidally stable dispersions of from 0.5 to 50% by weightconcentration.

3. The method of finishing textile materials which cornprises treatingsaid material With a finishing aqueous dispersion of 1% to 20% by weightof substantially pure dextran having a molecular weight of about 5000 toabout 50,000 as determined by light scattering measurements, a molecularstructural repeating alpha-1,6 to non-alpha-1,6 linkages ratio of 1.9:1to 30:1, and which forms, in wa ter, at ordinary temperatures,colloidally stable dispersions of, by weight, 0.5 to 50% concentration,removing excess treating medium from the fibrous material, and dryingand pressing the material under heating whereby the ma terial acquires asmooth, glossy surface finish substantially free from streaks, blotchesand discoloration without the application of starch thereto.

4. Finished, unstarched, hot-pressed textile material carrying afinishing film of a substantially pure dextran of molecular weight about5000 to about 50,000 as determined by light scattering measurements, amolecular structural repeating alpha-1,6 to non-alpha-1,6 linkages ratiobetween 1.9:1 and 30:1 and which forms, in water, at ordinarytemperatures, colloidally stable aqueous disper- 7 sions of 0.5% to 50%by weight concentration, said hotpressed fabric having a smooth, glossysurface finish sub stantially free from streaks, blotches anddiscoloration.

References Cited in the file of this patent UNITED STATES PATENTS 8Griinwall et a1. July 7, 1953 Deniston Apr. 6, 1954 OTHER REFERENCES

1. AS A FINISHING AGENT FOR TEXTILE MATERIALS TO PROVIDE SAID MATERIALS, WITHOUT LOSS OF THE ESSENTIAL FLEXIBILITY OF THE TEXTILE, AND WITHOUT THE APPLICATION OF STARCH THERETO, WITH A SMOOTH GLOSSY SURFACE FINISH SUBSTANTIALLY FREE FROM STREAKS, BLOTCHES AND DISCOLORATION ON HOT-PRESSING THEREOF AFTER APPLICATION OF A SOLUTION OF THE FINISHING AGENT THERETO, AND DRYING OF THE TEXTILE, A SUBSTANTIALLY PURE, DRY, PARTICULATE DEXTRAN HAVING A MOLECULAR WEIGHT OF ABOUT 5000 TO ABOUT 50,000, AS DETERMINED BY LIGHT SCATTERING MEASUREMENTS, A MOLECULAR STRUCTURAL REPEATING ALPHA-1,6 TO NON-ALPHA-1,6 LINKAGES RATIO OF 1.9:1 TO 30:1 AND WHICH FORMS, IN WATER, AND AT ORDINARY TEMPERATURES, COLLOIDALLY STABLE DISPERSIONS OF FROM 0.5% TO 50% BY WEIGHT CONCENTRATION. 